I bought a cheap receiver with speakers combo two days ago this one to be exact.

I have the HTPC hooked up by HDMI, but the sound actually has to be separate, so that is hooked up by spdif. the cable box is your normal red/white/yellow connection. The problem I am having is that I get a distinct buzzing sound when I watch cable, but no such buzzing when using the HTPC. Any ideas what could be causing this? Would the cables be a culprit for this? I don't want to spend more money if I don't have to.

Any chance you can upgrade your cable box? I recently discovered that I could get an HD box from the cable company for the same monthly rental price as I was paying for the crappy regular box. The HD box has DVI video output and Optical audio out. I can't believe how much better the sound is over Optical compared to RCA.

I'm gonna replace the cable box tomorrow (since now I get absolutely no sound) and see if it still happens. Rogers gives you nothing for free, so an upgrade in cable box means a grade up in monthly price.

It turned out to be the cable box screwing everything up. I changed the box and now the re is no buzzing sound.

Strange things happen. The mobo in my HTPC died. (I put the 690G board back in it for absolutely no reason and now it died). I bought an X2-7550 and a Gigabyte 785G board. After installing all the drivers (Realtek HD Audio), I am only getting 2-channel sound. The 690G board was giving 5.1 channel sound. I am using the SPDIF connection to my receiver.

Any suggestions on that? Anyone think I have to buy a soundcard? I REALLY don't want to do that!!!

I've pretty much tried everything I can find on the internet, that fits my current problem - so it looks like I will have to buy a sound card. The Xonar stuff is just too expensive, so the vanilla X-Fi with SP/dif on it is my only option. This really sucks!!!! I honestly thought that the optical output pushed all of the signals out in surround sound as a standard instead of using all of the jacks for surround sound to work. I'm still a little confused about all of that.

Seriously, the board is very modern, and there is an SPDIF connector, so I'm almost 100% certain the capability is there. So before you run out and buy more hardware...

What media player are you using? What codecs? If you use Media Player Classic - Home Theatre , and/or the ffdshow codec, there are alternatives in there to just pass on any digital source, eg. DD5.1 or DTS. Or in the case of ffdshow, even expand stereo sources to DD5.1.

Digital output is usually also an output device of its own. Check Sound in the Windows Control Panel if there is one. If there is, you should be able to set what output device to use in most media players. And if you're in XP, check the advanced settings in the mixer.

There are no relevant settings in the Realtek control panel?

However, you won't be able to output the newer "HD" sources, eg. TrueHD and such, through SPDIF. If you want that, you'll need to use an HDMI cable and pass it through the receiver.

What little info I've been able to find indicates that you may be missing something called the "Microsoft UAA High Definition Audio Class Driver". Do you have any unrecognized devices in Device Manager?

Edit: Fixed typo -- should be UAA not UUA.

The years just pass like trains. I wave, but they don't slow down.-- Steven Wilson

AC3filter is another option as well. There are lots of ways to get 5.1 sent out over spdif - It only becomes a bit iffy if you want to experience the HD codecs in their full quality or do something interactive like play games. Multimedia use should be no problem at all as long as you get everything configured properly.

For 5.1 sound, you need to pass through or generate on the fly AC3 and DTS streams. There's normally a checkbox in the driver to enable passthrough. ffdshow audio or ac3filter both offer the ability to exert a bit more control over the process. They can also encode AC3 for situations where you have multichannel audio that's not something you can send to your receiver over spdif (i.e. anything other than AC3/DTS, and with some, generally older, equipment, anything other than AC3).